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Message-Id: <20190919142228.5483-8-david@redhat.com>
Date: Thu, 19 Sep 2019 16:22:26 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, virtualization@...ts.linux-foundation.org,
Andrea Arcangeli <aarcange@...hat.com>,
David Hildenbrand <david@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Oscar Salvador <osalvador@...e.de>,
Michal Hocko <mhocko@...nel.org>,
Igor Mammedov <imammedo@...hat.com>,
Dave Young <dyoung@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
Pavel Tatashin <pasha.tatashin@...een.com>,
Stefan Hajnoczi <stefanha@...hat.com>,
Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH RFC v3 7/9] virtio-mem: Allow to offline partially unplugged memory blocks
Dropping the reference count of PageOffline() pages allows offlining
code to skip them. However, we also have to convert PG_reserved to
another flag - let's use PG_dirty - so has_unmovable_pages() will
properly handle them. PG_reserved pages get detected as unmovable right
away.
We need the flag to see if we are onlining pages the first time, or if
we allocated them via alloc_contig_range().
Properly take care of offlining code also modifying the stats and
special handling in case the driver gets unloaded.
Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Igor Mammedov <imammedo@...hat.com>
Cc: Dave Young <dyoung@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: Stefan Hajnoczi <stefanha@...hat.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
drivers/virtio/virtio_mem.c | 102 ++++++++++++++++++++++++++++++++----
1 file changed, 92 insertions(+), 10 deletions(-)
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 91052a37d10d..9cb31459b211 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -561,6 +561,30 @@ static void virtio_mem_notify_online(struct virtio_mem *vm, unsigned long mb_id,
virtio_mem_retry(vm);
}
+/*
+ * When we unplug subblocks, we already modify stats (e.g., subtract them
+ * from totalram_pages). Offlining code will modify the stats, too. So
+ * properly fixup the stats when GOING_OFFLINE and revert that when
+ * CANCEL_OFFLINE.
+ */
+static void virtio_mem_mb_going_offline_fixup_stats(struct virtio_mem *vm,
+ unsigned long mb_id,
+ bool cancel)
+{
+ const unsigned long nr_pages = PFN_DOWN(vm->subblock_size);
+ int sb_id;
+
+ for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
+ if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
+ continue;
+
+ if (cancel)
+ totalram_pages_add(-nr_pages);
+ else
+ totalram_pages_add(nr_pages);
+ }
+}
+
/*
* This callback will either be called synchonously from add_memory() or
* asynchronously (e.g., triggered via user space). We have to be careful
@@ -608,6 +632,7 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
mutex_lock(&vm->hotplug_mutex);
vm->hotplug_active = true;
}
+ virtio_mem_mb_going_offline_fixup_stats(vm, mb_id, false);
break;
case MEM_GOING_ONLINE:
spin_lock_irq(&vm->removal_lock);
@@ -633,6 +658,8 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
mutex_unlock(&vm->hotplug_mutex);
break;
case MEM_CANCEL_OFFLINE:
+ virtio_mem_mb_going_offline_fixup_stats(vm, mb_id, true);
+ /* fall through */
case MEM_CANCEL_ONLINE:
/* We might not get a MEM_GOING* if somebody else canceled */
if (vm->hotplug_active) {
@@ -648,23 +675,55 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
}
/*
- * Set a range of pages PG_offline.
+ * Convert PG_reserved to PG_dirty. Needed to allow isolation code to
+ * not immediately consider them as unmovable.
+ */
+static void virtio_mem_reserved_to_dirty(unsigned long pfn,
+ unsigned int nr_pages)
+{
+ for (; nr_pages--; pfn++) {
+ SetPageDirty(pfn_to_page(pfn));
+ ClearPageReserved(pfn_to_page(pfn));
+ }
+}
+
+/*
+ * Convert PG_dirty to PG_reserved. Needed so generic_online_page()
+ * works correctly.
+ */
+static void virtio_mem_dirty_to_reserved(unsigned long pfn,
+ unsigned int nr_pages)
+{
+ for (; nr_pages--; pfn++) {
+ SetPageReserved(pfn_to_page(pfn));
+ ClearPageDirty(pfn_to_page(pfn));
+ }
+}
+
+/*
+ * Set a range of pages PG_offline and drop the reference. The dropped
+ * reference (0) and the flag allows isolation code to isolate this range
+ * and offline code to offline it.
*/
static void virtio_mem_set_fake_offline(unsigned long pfn,
unsigned int nr_pages)
{
- for (; nr_pages--; pfn++)
+ for (; nr_pages--; pfn++) {
__SetPageOffline(pfn_to_page(pfn));
+ page_ref_dec(pfn_to_page(pfn));
+ }
}
/*
- * Clear PG_offline from a range of pages.
+ * Get a reference and clear PG_offline from a range of pages.
*/
static void virtio_mem_clear_fake_offline(unsigned long pfn,
unsigned int nr_pages)
{
- for (; nr_pages--; pfn++)
+ for (; nr_pages--; pfn++) {
+ page_ref_inc(pfn_to_page(pfn));
__ClearPageOffline(pfn_to_page(pfn));
+ }
}
/*
@@ -679,7 +738,7 @@ static void virtio_mem_fake_online(unsigned long pfn, unsigned int nr_pages)
/*
* We are always called with subblock granularity, which is at least
* aligned to MAX_ORDER - 1. All pages in a subblock are either
- * reserved or not.
+ * PG_dirty (converted PG_reserved) or not.
*/
BUG_ON(!IS_ALIGNED(pfn, 1 << order));
BUG_ON(!IS_ALIGNED(nr_pages, 1 << order));
@@ -690,13 +749,14 @@ static void virtio_mem_fake_online(unsigned long pfn, unsigned int nr_pages)
struct page *page = pfn_to_page(pfn + i);
/*
- * If the page is reserved, it was kept fake-offline when
+ * If the page is PG_dirty, it was kept fake-offline when
* onlining the memory block. Otherwise, it was allocated
* using alloc_contig_range().
*/
- if (PageReserved(page))
+ if (PageDirty(page)) {
+ virtio_mem_dirty_to_reserved(pfn + i, 1 << order);
generic_online_page(page, order);
- else {
+ } else {
free_contig_range(pfn + i, 1 << order);
totalram_pages_add(1 << order);
}
@@ -728,8 +788,10 @@ static void virtio_mem_online_page_cb(struct page *page, unsigned int order)
*/
if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
generic_online_page(page, order);
- else
+ else {
virtio_mem_set_fake_offline(PFN_DOWN(addr), 1 << order);
+ virtio_mem_reserved_to_dirty(PFN_DOWN(addr), 1 << order);
+ }
rcu_read_unlock();
return;
}
@@ -1674,7 +1736,8 @@ static int virtio_mem_probe(struct virtio_device *vdev)
static void virtio_mem_remove(struct virtio_device *vdev)
{
struct virtio_mem *vm = vdev->priv;
- unsigned long mb_id;
+ unsigned long nr_pages = PFN_DOWN(vm->subblock_size);
+ unsigned long pfn, mb_id, sb_id;
int rc;
/*
@@ -1701,6 +1764,25 @@ static void virtio_mem_remove(struct virtio_device *vdev)
BUG_ON(rc);
mutex_lock(&vm->hotplug_mutex);
}
+ /*
+ * After we unregistered our callbacks, user space can offline +
+ * re-online partially plugged online blocks. Make sure they can't
+ * get offlined by getting a reference. Also, restore PG_reserved.
+ */
+ virtio_mem_for_each_mb_state(vm, mb_id,
+ VIRTIO_MEM_MB_STATE_ONLINE_PARTIAL) {
+ for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
+ if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
+ continue;
+ pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
+ sb_id * vm->subblock_size);
+
+ if (PageDirty(pfn_to_page(pfn)))
+ virtio_mem_dirty_to_reserved(pfn, nr_pages);
+ for (; nr_pages--; pfn++)
+ page_ref_inc(pfn_to_page(pfn));
+ }
+ }
mutex_unlock(&vm->hotplug_mutex);
/* unregister callbacks */
--
2.21.0
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